This invention relates to a separation process. In particular, it relates to fractional distillation of a mixture containing acetone and at least one four-carbon atom hydrocarbon.
Mixtures of acetone and hydrocarbons containing four-carbon atoms are difficult to separate by conventional fractional distillation because of close boiling points of the component and/or because of the formation of azeotropes. Yet, such separation must be achieved as one of the steps in some commercial applications. For example, in the process of making butadiene from n-butane one of the intermediate steps -- first dehydrogenation -- results in creation of a mixture of n-butane and butylenes. Only butylenes are introduced into the second dehydrogenation zone; consequently, n-butane must be separated from butylenes. When the separation is carried out by extractive distillation with acetone, alone or in admixture with other solvents such as sulfolane, some of the acetone forms a mixture with n-butane, which must be separated if the ingredients are to be recycled. Failure to separate n-butane and acetone results in loss of acetone, which because the butane stream is relatively large represents an intolerable economic loss even at small concentrations of acetone.
One solution offered by the prior art is to contact the mixture with water. Acetone is selectively dissolved in water and then separated therefrom by distillation. The distillation of water-acetone mixture requires considerable amount of energy, thus making this approach economically and environmentally undesirable.
Another known approach is to employ an extractive solvent for separation of n-butane and acetone.
The present invention provides a novel method for separation of a mixture containing acetone and at least one hydrocarbon containing four-carbon atoms.
One object of the invention is to provide a method for separating acetone from hydrocarbons containing four-carbon atoms.
Another object of the invention is to provide a method for separating acetone from hydrocarbons containing four-carbon atoms without introduction of any other compounds, thus eliminating the possibility of contamination of separated products by additives.
Still another object of the invention is to provide a method for separating acetone from four-carbon hydrocarbons using conventional equipment for fractional distillation.
A further object of the invention is to prevent formation of azeotropes during fractional distillation of the mixture.
Still another object of the invention is to separate trace amounts of acetone from at least one four-carbon hydrocarbon.
A still further object of the invention is to simplify and improve the process of separating hydrocarbons containing four-carbon atoms from each other or one another using extractive distillation with acetone, by providing an improved way to separate acetone from the hydrocarbons after the extractive distillation step is completed.